243913981 has 4 divisors (see below), whose sum is σ = 243971200. Its totient is φ = 243856764.

The previous prime is 243913949. The next prime is 243913993. The reversal of 243913981 is 189319342.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 189319342 = 2 ⋅94659671.

It is a cyclic number.

It is not a de Polignac number, because 243913981 - 2⁵ = 243913949 is a prime.

It is a super-2 number, since 2×243913981² = 118988060254536722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (243913381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21651 + ... + 30928.

It is an arithmetic number, because the mean of its divisors is an integer number (60992800).

Almost surely, 2^243913981 is an apocalyptic number.

It is an amenable number.

243913981 is a deficient number, since it is larger than the sum of its proper divisors (57219).

243913981 is an equidigital number, since it uses as much as digits as its factorization.

243913981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57218.

The product of its digits is 46656, while the sum is 40.

The square root of 243913981 is about 15617.7457080079. The cubic root of 243913981 is about 624.8065372416.

The spelling of 243913981 in words is "two hundred forty-three million, nine hundred thirteen thousand, nine hundred eighty-one".